Re: Terrestrial QRM to FM satellites

At 06:39 AM 9/21/2007, Scott Wilson wrote:
> > There are apparently several stations.
>
>How sure is everyone that the QRM is on the uplink frequency? I have
>noticed some QRM, but it's usually MUCH stronger than the downlink, and
>will almost always completely over power the satellite signal. I've just
>assumed that it's local 70cm activity from some locals who don't know any
>better.
Well, there are ways of telling. Doppler shift is one. Does the QRM
follow the Doppler shift? Then there's the issue of uplink
interference. If you have a keen ear, it is possible to tell by
subtle differences in the audio whether the signal is on the uplink
or downlink, especially when you're running headphones. Similarly,
it's also possible to tell if you are experiencing downlink problems
or if the other station is not making the uplink, if you know what to
listen for (without looking at the S meter).
The above (except for Doppler shift, of course) also apply to
terrestrial repeaters.
73 de VK3JED
http://vkradio.com
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